Q83.Which of the following are arranged in an increasing order of their bond strengths ? (1) O−2 < O2 < O+2 < O2−2 (2) O2−2 < O−2 < O2 < O+2 (3) O−2 < O2−2 < O2 < O+2 (4) O+2 < O2 < O−2 < O2−2

Q84.Which of the following statements is true ? (1) HF is less polar than HBr (2) absolutely pure water does not contain any ions (3) chemical bond formation take place when forces (4) in covalency transference of electron takes place of attraction overcome the forces of repulsion

Q85.For an ideal gas, number of moles per litre in terms of its pressure P, gas contant R and temperature T is (1) PT/R (2) PRT (3) P/RT (4) RT/P

Q88.Which one of the following pairs of molecules will have permanent dipole moments for both members? (1) NO2 and CO2 (2) NO2 and O3 (3) SiF4 and CO2 (4) SiF4 and NO2